Comparative effects of aspirin and enteric-coated aspirin on loss of chromium 51-labeled erythrocytes from the gastrointestinal tract.

Sodium chromate Cr 51 was used to label red blood cells of 19 healthy male volunteers, whose stools were collected for four days before and four days during oral administration of either uncoated (N = 9) or enteric-coated (N = 10) aspirin. Each subject received 2.925 gm/day of aspirin, in three equal doses separated by eight-hour intervals, for a total of seven days. During drug use, stools were collected on days 4 through 7. Fecal blood content, estimated by measuring radioactivity in the stools, was significantly higher (P less than 0.001) during use of either type of aspirin than at baseline, but losses measured during use of the coated aspirin (mean, 1.54 ml/day) were significantly lower (P less than 0.001) than those measured during use of the uncoated aspirin (mean, 4.33 ml/day). The two types of aspirin produced equivalent serum concentrations of salicylates. We conclude that enteric-coated aspirin reduces gastrointestinal blood loss.